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2015 Vol. 41, No. 11

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2015 Year 41 Volume 11 Issue E-journal
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Trajectory linearization control based tracking guidance design for entry flight
SHEN Zuojun, ZHU Guodong
2015, 41(11): 1975-1982. doi: 10.13700/j.bh.1001-5965.2014.0424
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A novel use of trajectory linearization control (TLC) method was introduced in the guidance law design for hypersonic vehicle entry flight. By exploiting the inherent characteristics of time scale separation of entry vehicle dynamics, altitude and velocity could be controlled separately via outer and inner loop design. In the outer loop, path angle was used as pseudo-control for controlling the altitude. In the inner loop, the flight path angle command and velocity were tracked using bank angle and angle of attack as controls. A linear time-varying controller was designed for the feedback loop to stabilize the error dynamics. Feedback gains were computed online and are the symbolical functions of reference trajectory, therefore no explicit gain scheduling or mode-switching were needed. Extensive dispersion simulations show that this guidance algorithm can achieve precise trajectory tracking and is trajectory-independent. The simulations also show that an integrated entry guidance approach which combines the use of TLC-based tracking guidance law design and on-board reference trajectory planning can significantly enhance the autonomy and adaptability of entry flight.
Multi-mode vibration suppression of clamped plates based on piezoelectric networks
LI Lin, LI Jun, YI Kaijun
2015, 41(11): 1983-1993. doi: 10.13700/j.bh.1001-5965.2014.0703
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The exact solutions for transverse free vibrations of a clamped plate were adopted as the modal coordinates to solve the given electromechanical coupled kinetic equations of clamped piezo electro mechanical-plate in modal space. After the computational analysis was conducted for harmonic response of the clamped piezo electro mechanical-plate which was stimulated under single-point excitation force, the optimal parameters of electrical components in piezoelectric networks used to suppress different resonances were obtained. For the clamped piezo electro mechanical-plate with parallel resistors and inductors, it has more than one local optimal parameters comparing with a simply supported plate. The clamped piezo electro mechanical-plate has the ability to suppress multimode vibration by analyzing the effectiveness of these optimal parameters on other resonances. In addition, the effectiveness is more sensitive to inductance comparing with resistance. The clamped piezo electro mechanical-plate with parallel resistors and inductors is more effective than piezo electro mechanical-plate only with resistors in reducing resonant response at single resonant frequency, while the multiple-mode vibration suppression effectiveness of it with parallel resistors and inductors will be decreased.
An UAV air-combat decision expert system based on receding horizon control
FU Li, XIE Fuhuai, MENG Guanglei, WANG Dongzheng
2015, 41(11): 1994-1999. doi: 10.13700/j.bh.1001-5965.2014.0726
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Aiming at the poor adaptability of expert system in air combat, a maneuvering decision algorithm based on the receding horizon control (RHC) method was proposed to improve the air combat maneuvering decision-making expert system. Firstly, the optimal control problem was systematically analyzed in the air combat maneuvering decision-making expert system. The system state equation, the index function and the control constraints of the maneuvering decision-making optimal control model were established. On this basis, according to the principle of the RHC method, the whole air combat process was divided into some sequential ones with the finite time horizon. In each time horizon, the optimal control model of the maneuvering decision-making expert system was solved to conduct air combat maneuvering decisions with initial state updated. The process was repeated until the air combat was over. The simulation result shows that, through solving the RHC optimal control model of the air combat maneuvering decision-making expert system, the unmanned aerial vehicle (UAV) can rapidly take effective maneuvering decisions in the case of expert system failure.
Two dimensional dynamics of continuous cislunar payload transfer system considering structural deviation effect
QI Naiming, YANG Yong, HUANG Panxing, SUN Kang, HAN Bing
2015, 41(11): 2000-2009. doi: 10.13700/j.bh.1001-5965.2014.0730
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Based on the motorized momentum exchange tether (MMET), with the principle of momentum exchange and by considering the structural deviation (including the tether length deviation and payload mass deviation), the two dimensional error dynamics of continuous cislunar payloads transferring system (CCPTS) was built by Lagrange method and its numerical simulated solution was solved by Mathematica software. Under the conditions of existing the tether length deviation and payload mass deviation, the dynamic simulations of the CCPTS were presented. It is shown that tether length deviation and payload mass deviation have similar influence on CCPTS's dynamics (including generalized coordinates and generalized velocity). With the increment of tether length deviation or payload mass deviation, the maximum of the CCPTS's generalized coordinates' deviation and generalized velocities' deviation increases linearly. However, the maximum of the CCPTS's generalized accelerations have no evident linear relation with the structure deviation of the CCPTS. Lastly, the external torque can weaken the influence degree of the structure deviation of the CCPTS on the dynamic parameters.
Vehicle height adjustment of closed-loop air circuit laterally interconnected air suspension system
JIANG Hong, YANG Yongfu, YU Pengfei, XU Xing, LI Mei
2015, 41(11): 2010-2016. doi: 10.13700/j.bh.1001-5965.2014.0759
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In order to further improve the dynamic and energy-economic performance of air suspension, a closed-loop air circuit laterally interconnected air suspension structure which combines the advantages of both interconnected air suspension system and closed-loop air circuit air suspension height control system with high and low pressure chambers was proposed. In order to deal with the portability defects caused by traditional air suspension height control strategy when it's applied to the interconnected suspension system, a special proportion integration differentiation-pulse-width modulation (PID-PWM) height control strategy designed for laterally interconnected air suspension was proposed and a corresponding mathematical model was established for simulation study via MATLAB/Simulink. The simulation results show that the control strategy works effectively, the overshoot phenomenon is avoided and the portability defects have been solved. A height adjustment experiment is carried out on a test bench and the impact of different initial pressure of gas chamber on the charging/discharging time as well as the control error during the vehicle height adjustment were studied. The experimental results show that the control strategy for the closed-loop air circuit laterally interconnected air suspension system can adjust the vehicle body height rapidly and accurately. The correctness of the mathematical model and the validity of control strategy are verified. The study about the impact of gas chamber initial pressure provides a theoretical basis for the setting of the vehicle height adjustment system parameters.
Image-based underwater 3D reconstruction with single viewpoint adjustment camera model
WEI Yingmei, KANG Lai
2015, 41(11): 2017-2022. doi: 10.13700/j.bh.1001-5965.2015.0059
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In underwater imaging, the light ray associated with each scene point goes through different media with different refractive indices, which introduces refractive distortion in underwater images. Such distortion reduces the accuracy of image-based 3D reconstruction based on traditional single viewpoint camera model. Based on theoretical analysis of the ability of a new single viewpoint adjustment camera model in compensating for refractive distortion, an efficient and automatic image-based underwater 3D reconstruction algorithm with non-linear optimization was proposed. The performance of the purposed method in terms of reconstruction efficiency and accuracy was examined quantitatively using both synthetic data and real images. The experimental results suggest that the proposed single viewpoint adjustment camera model can handle scene space distortion effectively and significantly improve the quality of traditional image-based underwater 3D reconstruction using single viewpoint camera model.
An LCP method for dynamics of planar-motion rigid-body with non-symmetric friction
WANG Xiaojun, WANG Qi
2015, 41(11): 2023-2028. doi: 10.13700/j.bh.1001-5965.2014.0765
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A modeling and numerical calculation method for the dynamics of the rigid-body in planar motion with contact, impact, symmetric and non-symmetric Coulomb's dry friction was presented based on the theory of contact mechanics and the arithmetic of linear complementarity problem (LCP). The local deformations in contact bodies were taken into account although bodies were assumed to be rigid. The normal contact forces were expressed as nonlinear functions of penetration depth and its speed. The friction law adopted symmetric or non-symmetric Coulomb's dry friction model. Firstly, by using the friction saturation, the positive and negative parts of the relative acceleration of contact points, the complementarity conditions and formulations about the friction law were given in order to determine state transitions of stick-slip in numerical method. Then, based on the event-driven scheme, the problems of detecting stick-slip state transitions and solving frictional forces in stick situation were formulated and solved as a linear complementarity problem. Finally, the numerical example of a planar-motion rigid-body was given to analyze its dynamical behaviour affected by symmetric or non-symmetric Coulomb's dry friction and shown that the proposed method was effective.
Effect of Zr content on properties of Ti-Zr-Cu-Ni filler metal and its brazed joint
GUO Wei, QI Dan, YANG Jianjun, LI Fei, HUA Yongping, YU Wenjun
2015, 41(11): 2029-2035. doi: 10.13700/j.bh.1001-5965.2014.0774
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Four kinds of titanium-based filler metals, Ti-5Zr-15Cu-15Ni, Ti-10Zr-15Cu-15Ni, Ti-15Zr-15Cu-15Ni and Ti-25Zr-15Cu-15Ni, were fabricated by electric arc melting method, and the four kinds of filler metals were used for vacuum brazing of Ti-6Al-4V plate lap joints. The melting characteristic and wettability of the filler metals on Ti-6Al-4V were tested, and the microstructures, microhardnesses and shear strengths of the brazed joints with different filler metals were tested and analyzed. The results show that the addition of Zr has an obvious effect on the melting temperature of Ti-Zr-Cu-Ni filler metal. The gap between solidus and liquidus temperatures is wide with much higher liqiudus temperature when the content of Zr is 5wt% or 25wt%. In contrast, the gap between solidus and liquidus temperatures is narrow with lower liquidus temperature when the content of Zr is 10wt% or 15wt%. Different from other compositions of filler metals, when the content of Zr is 25wt%, there are two obvious low temperature eutectic reactions during melting process, and the filler metal appears two spreading layers phenomenon during the wetting process. And much lower microhardness was attained in the brazed joint when the content of Zr is 15wt% or 25wt%. Considering the melting characteristic of the filler metals and the microhardness and shear strength of the brazed joints, the optimized composition of the filler metal is Ti-15Zr-15Cu-15Ni, and the shear strength of the brazed joint with this filler metal is 298 MPa.
Aircraft fuel measurement sensor optimal layout technology
YUAN Mei, HE Yiqiang, DONG Shaopeng, NIU Ben
2015, 41(11): 2036-2043. doi: 10.13700/j.bh.1001-5965.2014.0745
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It is very important for aircraft flight safety to accurately measure the remaining fuel in each fuel tank in real time. An aircraft fuel measurement sensor optimal layout method based on particle swarm optimization (PSO) was designed to improve aircraft fuel measurement accuracy. Firstly, the concept of the fuel entity was proposed, and two models were built including the complex wing fuel tank CAD model which had multi-chamber with inner clapboards and the fuel entity model in fuel tank. Secondly, the total fuel volumes of complex and irregular multi-chamber tanks were calculated at different aircraft attitudes based on the second development of Unigraphics NX (UG). Thirdly, the concept of the largest measurement range (LMR) of the aircraft fuel tanks was put forward, which was used as the goal to optimize the sensor layout. Finally, the boundary distance factor (BDF) was introduced to avoid settling the sensor too close to the fuel tank wall. The results show that the method can optimize the layout of several fuel sensors without being limited by the shape and size of the fuel tank, which can effectively avoid interference in the internal area of the tank, ensure fuel measurement continuity at different aircraft attitudes, and make the aircraft fuel measurable range reach a higher level.
Calculation of the astronauts' radiation dose from galactic cosmic ray
ZHANG Binquan, YU Qinglong, LIANG Jinbao, SUN Yueqiang, YANG Chuibai, ZHANG Shenyi
2015, 41(11): 2044-2051. doi: 10.13700/j.bh.1001-5965.2014.0712
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Radiation risk of astronauts during the flight in low earth orbit (LEO) and deep space exploration is mainly from the exposure of galactic cosmic ray (GCR). The radiation dose from GCR is the basis for the assessment of astronauts' radiation risk. In 2013, a new estimation method for the assessment of astronauts' radiation dose was presented by the International Committee on Radiological Protection (ICRP), so as to improve the assessment's accuracy of the radiation dose from heavy ions in space. Based on this method, a Monte Carlo program was developed for simulation of the particle transportation in materials and a voxel phantom of Chinese adult male was realized in this program to represent the astronaut. With this program, the fluence to dose conversion coefficients for the organs of astronauts were calculated for the isotropic exposure by particles with the atomic number from 1 to 92. The radiation dose to astronauts in LEO from GCR was also estimated.
Analysis and test research on influencing factors of drilling and coring quantity of lunar soil simulant
QUAN Qiquan, SHI Xiaomeng, TANG Dewei, JIANG Shengyuan, DENG Zongquan
2015, 41(11): 2052-2060. doi: 10.13700/j.bh.1001-5965.2014.0782
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During the design of drilling and coring mechanism for lunar exploration, a coring method based on a flexible tube can obtain slim continuous sample core, which enables high coring rate and preserves the stratification information of the subsurface samples. Since the complex movement of lunar soil particles during the flexible tube coring, there is no systemic method to analyze the factors that determine the coring quantity. The flowage of the lunar soil particles in flexible tube was analyzed and the coring model of the flexible tube based on the theory of limit equilibrium was established. The mechanical boundary conditions of the model were interactions between lunar soil and coring drill tools and among each part of lunar soil. The coring model described the dynamic process of lunar soil flowing from the outside of coring drill tools into the flexible tube. A numerical prediction method for coring rate was proposed based on the coring model. Drilling parameters, lunar soil properties and drill tool structure were analyzed as key influencing factors of coring rate. A verifying test with simulant of lunar soil HIT-LS1# and drill tools HIT-2 was implemented on a simulated drilling test-bed. The average error between the test results and the predicted results is less than 5%.
Inverse heat conduction problem for transient external heat flux inversion of spacecraft on orbit
SONG Xin, ZHANG Youwei, LIU Zijun
2015, 41(11): 2061-2066. doi: 10.13700/j.bh.1001-5965.2014.0719
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Spacecraft external heat flux is very important for researching deterioration law of thermal control coating on orbit, influence of various spatial factors on thermal control products, as well as plume thermal effect of spacecraft attitude and orbit control engine. However, there are many difficulties in direct heat flux measurement. Thus, the inverse heat conduction problem can be used to get results which can satisfy certain precision. Firstly, in order to deduce transient external heat flux of spacecraft on orbit from telemetry temperature of spacecraft equipment on orbit, inverse heat conduction problem mathematical model was set up and solved by the conjugate gradient method. Iterative process of conjugate gradient method was improved according to physics concept in order to increase its anti instabilit. Then, two numerical tests were used for the purpose of checking mathematical model effect. The numerical tests could represent external heat flux change of most both earth-orbiting spacecraft and deep space exploration spacecraft. The maximum relative deviation between inversion value and true value is 2.9% except step change data. Inversion results of the mathematical model is very good. Furthermore, satisfied results can be obtained by processing data analysis for absorbed external heat flux at step change location.
IMA application development based on Harmony system engineering
XU Wen, XIONG Zhiyong, ZHANG Guoquan
2015, 41(11): 2067-2077. doi: 10.13700/j.bh.1001-5965.2014.0741
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Integration modular avionics (IMA) system application development with Harmony system engineering (SE) modeling method was introduced, Rhapsody was used as the system design tool with Harmony profile to create a software model based on the IMA application requirements, and the system use case diagrams, activity diagrams, sequence diagrams, internal block diagrams and state diagrams were analyzed. With the model, the IMA application development process based on VxWorks 653 operation system(OS)was specified, including module OS build, partition OS build, application build and integration build, and test the IMA application. In module OS build process, it was focused on the development of core OS Makefile. In partition OS build process, it was focused on the development of partition OS configuration table and its Makefile. In application build process, it was focused on the development of application source code, application configuration table and its Makefile. In integration build process, it was focused on the development of module configuration table and its Makefile. The application was tested by loading it into the IMA module, the application's running state was consistent with the Harmony software model.
Wing rock motion induced by forebody asymmetric vortices in pitch-up
XU Siwen, DENG Xueying, WANG Yankui
2015, 41(11): 2078-2084. doi: 10.13700/j.bh.1001-5965.2014.0707
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Aiming to the issue that the angle of attack was usually fixed rather than pitched-up in the previous researches about the wing rock induced by forebody asymmetric vortices, series of wind tunnel experiments were conducted in Beihang University D4 wind tunnel over the configuration of a pointed ogive-cylindrical body with 30° swept wings. Effect of pitch rate on wing rock motion as well as the mechanism of that was first studied through wing rock experiments in different pitch rates. The flow mechanism of wing rock in high rate pitch-up was then studied through the surface pressure measurements during the dynamic wing rock. Experimental results show that, as the wing rock motion time reduces with increase of pitch rate, the motion patterns of wing rock are different in three different intervals of pitch rate. The sinusoidal-like motion, which is totally different from the motion at static angle of attack, would occur in the third interval with high rate pitch-up. The variation of forebody flow with angle of attack, instead of the variation of forebody flow with roll angle, is found to be responsible for the sinusoidal-like motion in high rate pitch-up. Hence, the flow mechanism of wing rock in pitch-up is greatly different from that at static angle of attack.
LADRC-based attitude decoupling control for helicopter and parameters tuning
WU Chao, WANG Haowen, JIANG Chen, ZHANG Yuwen, NI Xianping
2015, 41(11): 2085-2094. doi: 10.13700/j.bh.1001-5965.2014.0710
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To meet the ADS-33E-PRF flight quality and effectively overcome the influence of external disturbance, an attitude control strategy based on a linear active disturbance rejection control (LADRC) is proposed for helicopter. Flight dynamics model of UH-60A and the wind model were established. UH-60A was trimmed for verifying accuracy of dynamic model and trim algorithm. Helicopter attitude decoupling control loop based on the single input/single output second-order LADRC controller was set up with stabilization feedback loop. The controller parameter tuning problem was transformed into constrained optimization problem in time and frequency domain according to quality requirement of ADS-33E-PRF. Combining H-infinity synthesis algorithm and steepest descent algorithm, the optimization of parameters was calculated. Quality assessment of attitude control was made and the control loop was applied to the attitude hold control simulation in atmospheric disturbance. The results of simulation and quality evaluation show that the attitude control system based on LADRC has good decoupling performance and capability of anti-disturbance.
Sliding mode guidance law for KKV based on collision course
YANG Xu, ZHANG Jiao, LIU Yuanxiang
2015, 41(11): 2095-2102. doi: 10.13700/j.bh.1001-5965.2014.0728
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Aimed at the problem of exoatmospheric kinetic kill vehicle(KKV) guidance law design for intercepting targets, a novel missile sliding mode guidance law with nonlinear disturbance observer (NDO) was derived base on collision course. Through steering angle of attack of missile, the direction of velocity of missile always pointed at the expected collision point. Missile could intercept the target with lower overload, faster speed via NDO, which was currently estimating and dynamically compensating to target acceleration. Moreover, comparison to the two interception strategies were obtained with interception trajectories, capture zones and velocity range. Another strategy was the sliding mode guidance law based on finite time convergence which aiming to steering the line of sight rate close to zero. The results show that the validities of the proposed sliding mode guidance law based on collision course in application for kinetic kill vehicle.
Design and comparative analysis of multistage compression cone-derived waverider and osculating cone waverider
LYU Zhenjun, WANG Jiangfeng
2015, 41(11): 2103-2109. doi: 10.13700/j.bh.1001-5965.2014.0740
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As a forebody of hypersonic vehicle which was powered by air-breathing scramjet, waverider not only showed its excellent aerodynamic performance, but also played the role of pre-compression to incoming flow for hypersonic vehicle. In order to further enhance the waverider forebody's pre-compression effect, a new design method for multistage compression waverider configuration was presented, based on theory of osculating cone proposed by Sobieczky. Multistage compression cone-derived waverider and osculating cone waverider which had multiple compressive surfaces were obtained by using the design method. Aerodynamics performance of three-stage compression cone-derived waverider and osculating cone waverider were compared and analyzed in the same design condition and with the same projection curve of forbody. The research results show that the design expectation is in well agreement with the result of numerical simulation. The design method of multistage compression waverider can be used to cone-derived waverider and osculating cone waverider.
Device design and implementation method of lunar soil simulant vacuum test
ZHANG Tao, AN Yinghe, DING Xilun
2015, 41(11): 2110-2115. doi: 10.13700/j.bh.1001-5965.2014.0753
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Drilling sample of lunar soil over depth of 2 m is the most important object of the third stage of China's lunar exploration project. For performance test and security validation of the drilling process, it is necessary to simulate a vacuum thermal environment which is close to lunar surface and then to carry out the simulation test. A test device for lunar soil simulant in vacuum condition was designed and the pumping method was studied. The vacuum degree, under the condition of mechanical pump, influenced by pumping velocity, sample volume, water content, density and temperature was analyzed. Furthermore, with comparing the effect of methods which pumped from the top and the bottom of the lunar simulants vessel, the most efficient method to maintain the density of lunar soil simulants was put forwarded. The research makes some contribution to the construction of lunar vacuum thermal environment simulator.
Coordinated standoff target tracking using two UAVs with only bearing measurement
ZHU Qian, ZHOU Rui, DONG Zhuoning, LI Hao
2015, 41(11): 2116-2123. doi: 10.13700/j.bh.1001-5965.2014.0716
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A novel method for a random moving target coordinated standoff tracking was proposed to maximize the target position estimation precision by two unmanned aerial vehicles (UAVs) equipped with only bearing sensor. The analytical relationship model between the UAV observation geometry configuration and the root mean square error (RMSE) of target position estimation, which is chosen as performance index, was established, and thus the optimal UAV observation geometry configuration was obtained. Extended information filter was used to implement target states fusion and estimation. The optimal cooperative observation geometry configuration was implemented using online distributed nonlinear model predictive control (NMPC), considering the constraints of UAV platform dynamic performances, collision avoiding, and security distance. The simulation results demonstrated the pair of UAV effectively maintained the optimal observation geometry configuration and coordinated standoff target tracking performance in real-time.
Fault diagnosis method based on extension case-based reasoning
WEN Tianzhu, XU Aiqiang, SUN Weichao
2015, 41(11): 2124-2130. doi: 10.13700/j.bh.1001-5965.2014.0736
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Extension case-based reasoning is a kind of knowledge reasoning method which is the combination of the extenics and case-based reasoning. Firstly, the representation of extension case using compound element was introduced, and the similarity computing method of fault symptom with interval value was given. Secondly, the reasoning process of extension case was analyzed; in the retrieve of extension cases, rough set method was adopted to confirm weight of fault symptom, and search strategy guided by rules was proposed; in the reuse of extension cases, conductive transformation was adopted to fulfill the reuse of extension case according to different search results; in the revise of extension cases, increasing and decreasing transform were adopted to add or delete fault symptoms of reused extension case and change their weight; in the retain of extension cases, three retain modes of revised extension case were discussed, including adding, deleting and replacing. Thirdly, the fault diagnosis process of this method was explained by an application case, and the time complexity of extension case retrieve was analyzed. By the comparison of the proposed search strategy and global search strategy, it is known that using the proposed search strategy can increase search efficiency and improve diagnosis speed.
Adaptive decoupling control of a MIMO system based on fuzzy neural networks
BAI Chen, FAN Yao, REN Zhang, YANG Peng
2015, 41(11): 2131-2136. doi: 10.13700/j.bh.1001-5965.2014.0758
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According to the control problem of a class of uncertain multiple-input multiple-output (MIMO) nonlinear systems, an adaptive decoupling control approach based on fuzzy neural networks was proposed. Firstly, a sub-channel decoupling control law of MIMO nonlinear systems was designed using decentralized control theory and feedback linearization approach. Secondly, the approximation of the system coupling terms and uncertainty terms were obtained by a fuzzy neural networks observer and compensated into the control law as compensation signal. It was proved that the control law, the observer and the weighted vector adaptive law could guarantee the uniform convergence of the errors of the output variable, the observer variable and the weighted vector finally. Simulations were carried on a typical uncertain MIMO system. The proposed method was compared with a traditional output feedback control method without adding compensation control signal. The simulation results show that the influence caused by coupling among the channels and uncertainty is eliminated by the compensation control and the observer errors can converge. The results validate the effectiveness and stability of the proposed control approach.
Strategy of removing space debris using ground-based lasers
WANG Chenglin, ZHANG Yan, WANG Kunpeng
2015, 41(11): 2137-2143. doi: 10.13700/j.bh.1001-5965.2014.0696
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The removal strategy of space debris is one of the most key technologies to achieve the goal of clearing space debris in a wide range of sizes from 1 to 10 cm actively using ground-based lasers. In order to develop an effective strategy for removing space debris, we firstly studied on the influences, which the changes of different velocity components had on the altitude of new orbit's perigee, finding that the same velocity increment along different velocity components has different effects on lowering the altitude of perigee. And then combined with the geometrical and physical of ground-based lasers, the constraint conditions that determine the area of orbit transfer were deduced. Finally, a general strategy, removing space debris in the way of continuous impulse orbit transfer using ground-based lasers, was proposed based on those mentioned above. Moreover, space debris removal using ground-based lasers is realized and the effectiveness of the clearing strategy is also verified through simulation experiments.
Analysis of transient vibration of single-thick-disk rotor crossing two orders of critical speeds
LIU Zheng, WANG Jianjun
2015, 41(11): 2144-2157. doi: 10.13700/j.bh.1001-5965.2014.0699
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The special structure of drum type compressor of aero-engine, which can be simplified as a thick-disk rotor system whose radial moment of inertia is greater than the axial one, has two inherent frequencies when whirling forward. Transient response to unbalance exciting force of single, thick-disk rotor crossing two orders of critical speeds in constant angular acceleration and constant working power was calculated respectively, and the nonlinear coupling between the thick-disk rotor and energy occurred at the latter. The results show that the low order vibration shape of single, thick-disk rotor is shaft's bend, the higher one disk's inclination, wherein the higher order mode is unique feature of thick-disk rotor; when rotor crosses the critical speed, its transient vibration is composed of free vibration and forced vibration; when the power is not enough to provide the rotor crossing critical speeds, the coupling between external energy and the rotor system will appear, resulting in a sharp increasing stall phenomenon.
Preparation of layered MoS2/Graphene films and their electrocatalytic performance of hydrogen generation
YANG Yang, XU Di, WU Qingyong, XIANG Min, DIAO Peng
2015, 41(11): 2158-2165. doi: 10.13700/j.bh.1001-5965.2014.0709
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MoS2/Graphene electrocatalysts which were used for water-electrolytic hydrogen making were synthesized using a hydrothermal method among which NH2CSNH2(thiourea) was served as both the source of sulfur and the reductive agent. MoS2/Graphene films prepared on fluorine-doped tin oxide (FTO) by spin coating method were applied for performance test of electrocatalytic water splitting. The study shows that the activity of MoS2 toward hydrogen evolution reaction improves as high as nearly 100% after coupling with graphene. The high catalytic activity of MoS2/Graphene was attributed to two aspects:firstly, the selective growth of layered MoS2 on graphene through chemical coupling afforded an abundance of catalytic active sites on MoS2 edges. Secondly, as a good conductive substrate, the graphene sheets can accelerate the electron transfer. The 12 layered MoS2/Graphene catalysts achieved the highest efficiency toward hydrogen evolution reaction with a current density up to -4.5 mA/cm2 at the overpotential of 0.2 V and an onset potential of 0.085 V in 0.5 mol/L H2SO4 solution. Hence, as a substitute for Pt family noble metal toward hydrogen evolution reaction, the layered MoS2/Graphene has broad application prospects.
Algorithm based-on dynamic Bayesian networks for repairable GO methodology model
FAN Dongming, REN Yi, LIU Linlin, LIU Shuzheng, FAN Jian, WANG Zili
2015, 41(11): 2166-2176. doi: 10.13700/j.bh.1001-5965.2014.0767
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GO methodology was an effective method of evaluating the reliability and the security of complex systems. Besides the capability to describe the sequence characteristics of multi-states, GO methodology was also capable of expressing complex dynamic repair behavior of the systems. For GO methodology models whose systems containing the dynamic repairable characteristic, a new algorithm based on the Bayesian networks was presented. The algorithm firstly mapped the repairable and unrepairable operators into dynamic Bayesian networks, and then mapped the whole model into Bayesian networks software to solve the problem. With the support of the mature algorithm and software, this new algorithm is capable not only of figuring out the curves of reliability that is changed over time but also the reliability index on the determined time point without caring about the shared signals. This new algorithm based on the Bayesian networks theory is governed by unified simple rules and it is quite convenient to apply in engineering.
Effect of attack angle on stability and transition in a swept-wing boundary layer
JING Zhenrong, SUN Pengpeng, HUANG Zhangfeng
2015, 41(11): 2177-2183. doi: 10.13700/j.bh.1001-5965.2014.0769
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Abstract:
Attack angle is one of the key parameters to the cross-flow instability of swept-wing boundary layers. For swept NACA0012 airfoil with infinite spanwise length, the basic flow field was calculated by solving the three-dimensional compressible Navier-Stokes equations numerically, the neutral curve and the evolution curve of growth rate were obtained by solving the Orr-Sommerfeld equation, the effect of attack angle on the cross-flow stability was analyzed by linear stability theory (LST), and the transition position was predicted by eN method. It is found that, the growth of unstable waves in the leeward is inhibited but enhanced in the windward. Transition firstly occurs in the windward, and the transition position predicted by eN method is about 0.1 to 0.2 of the chord length with the N factor of about 6 when the disturbance velocity is 0.05% of the free-stream velocity.
Roll maneuver control of robotic fish propelled by oscillating pectoral fins
GONG Zhao, CAI Yueri, BI Shusheng, MA Hongwei
2015, 41(11): 2184-2190. doi: 10.13700/j.bh.1001-5965.2014.0748
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Abstract:
Based on the practical requirements on the research of the roll maneuver control of robotic fish propelled by oscillating pectoral fins, a central pattern generator (CPG) based fuzzy control method was presented. Pectoral fins oscillating disciplines which drive the robotic fish roll were obtained by mimicking the pectoral fins oscillating pattern of natural prototype, and relative parameters were defined to quantitatively describe the disciplines. Based on the CPG model, a fuzzy method controller was built to achieve the roll motion control of robotic fish. Experiments were presented and the related results were analyzed in detail. Results show that the robotic fish rolls quickly to reach the target angle at the maximum angular velocity of 10(°)/s, and the steady state error is less than ±5°. Finally, with the combination of the roll maneuver control and the yaw control, the robotic fish can swim through a narrow space with the width of 1/2 wingspan,which shows the high maneuvering ability of the robotic fish propelled by oscillating pectoral fins.

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